1. Field of the Invention
The invention relates to a recording head and a recording apparatus using the recording head. More particularly, the invention relates to a recording head in which a plurality of recording elements arranged in a predetermined direction and a drive circuit to drive the recording elements are formed on a same element base substance and the recording elements are divisionally driven every plural blocks and to a recording apparatus using the recording head.
2. Related Background Art
For example, as information output apparatuses which are used for word processors, personal computers, facsimile apparatuses, and the like, recording apparatuses such as printers and the like for recording information such as desired characters, image, or the like onto a sheet-like recording medium such as paper, film, or the like are widely used.
Various systems have been known as recording systems of the printers. In recent years, among them, attention has been paid particularly to an ink jet system. The ink jet system has such various advantages that the information can be recorded onto a recording medium such as paper or the like in a contactless manner, a color image can be easily formed, it is silent, and the like.
As a construction of the recording apparatus of the ink jet recording system, a serial recording system in which the recording apparatus has a recording head for discharging ink in accordance with desired recording information and the recording is executed while reciprocatively scanning the recording head in the direction which crosses the feeding direction of the recording medium is widely used. The serial recording system has such advantages that it is reasonable in price, it can be easily miniaturized, and the like.
A method of discharging the ink by using a heat energy has been known as an ink discharging method in the ink jet recording system. In this case, in the recording head, an electrothermal converting element such as a heating element or the like is attached to a portion communicated with a discharge port for discharging an ink droplet. By supplying a current to the heating element for about a few microseconds, a bubble is generated in the ink and the ink droplet is discharged onto the recording medium by its pressure.
In such a recording head, a number of discharge ports and heating elements can be easily arranged at a high density, so that a high precision image can be recorded.
In such a recording head, if all of the heating elements are simultaneously driven, since a large current is momentarily supplied, a power source of a large capacity is necessary. Therefore, usually, tens to hundreds of heating elements are divided into a plurality of blocks and time-divisionally driven at slightly different timing every block, thereby suppressing a value of the current which flows momentarily to a small value.
By forming the drive circuit of the heating elements onto the element substrate of the recording head, the number of wirings between the recording head and the recording apparatus main body is reduced. An Si (silicon) wafer has widely been used as a material (element base substance) of the recording head element substrate having the heating elements and the drive circuits therein. An example in which the Si wafer is used as an element base substance has been disclosed in Japanese Patent Application Laid-Open No. 2002-321366.
Various constructions can be given as a construction of the circuit formed on the element substrate. An example of a layout construction of a typical recording head element substrate is shown in FIG. 6.
Referring to FIG. 6, two groups 623 and 624 for executing the ink discharging operation by signals from a recording apparatus main body (not shown) are symmetrically arranged so as to sandwich an ink supply port 600. Each of the groups 623 and 624 has: a terminal 621; a shift register 619; a latch circuit 617; a decoder 615; a wiring 605; gate circuits 603; a buffer 601; power transistors 609; and heating elements 611.
A clock and recording data in a serial format synchronized therewith are inputted from the recording apparatus to the recording head element substrate. The recording data is inputted to the terminal 621 of the recording head element substrate. The recording data is constructed by a data signal and a block signal. The data signal is a signal indicative of the block to be driven. The block signal is an encoded signal indicative of the heating element to be driven in the block.
Each bit of the recording data inputted to the terminal 621 shifts the shift register 619 synchronously with the clock and is held in the latch circuit 617. The portion of the block signal in the recording data held in the latch circuit 617 is decoded by the decoder 615 and outputted to the wiring 605. The portion of the data signal is directly outputted from the latch circuit 617 to the wiring 605.
A plurality of circuits each comprising the gate circuit 603, the power transistor 609, the heating element 611, and a level converter (not shown) are provided at the edge of the wiring 605. In the wiring 605, the portion showing selecting conditions of each heating element 611 is connected to each gate circuit 603. The gate circuit 603 is connected to the power transistor 609 through the level converter (not shown). The level converter is used to enhance driving ability of the power transistor 609 by stepping up an output of the gate circuit 603 and is driven by the buffer 601. The power transistor 609 is connected to the heating element 611 and the heating element 611 is driven by a signal from the power transistor 609.
With the construction as mentioned above, the recording head element substrate drives the heating elements 611 on the basis of the recording data from the recording apparatus and discharges the ink onto the recording medium.
In the conventional recording head having the recording head element substrate as shown in FIG. 6, generally, high picture quality and high processing speed are realized by increasing the number of heating elements. Specifically speaking, by increasing the number of bits of the data signal in the recording data, the number of heating elements which can simultaneously discharge the ink is increased, thereby raising a print speed.
Although an increase in number of heating elements 611 cannot be avoided, the number of power transistors 609 and the number of gate circuits 603 also increase in association with it. A size of the recording head element substrate increases in the layout direction of the heating elements 611 in association with the increase in number of heating elements.
Since the minimum time interval which is determined by discharging characteristics of the ink and at which the ink can be repetitively discharged from the same nozzle is equal to about tens of microseconds, there is a limitation in the increase in number of bits of the block signal in the recording data in order to increase the number of heating elements 611.
If the number of bits of the data signal is increased, the number of bits of each of the shift register 619 and the latch circuit 617 increases and the number of wirings included in the wiring 605 also increases. Thus, an area of the shift register 619 and latch circuit 617 arranged near the terminal 621 and, further, an area of the wiring 605 increase. The size of the recording head element substrate increases not only in the layout direction of the heating elements 611 but also in the direction perpendicular to the layout direction.
As mentioned above, in the construction of FIG. 6, when it is intended to realize high picture quality and a high speed, the number of head element substrates which can be obtained from one Si wafer decreases remarkably and costs of the head element substrate rise.
It is an object of the invention to provide a recording head whose costs are reduced by decreasing an area of an element substrate and a recording apparatus using such a recording head.